WASHINGTON - Home Covid-19 test kits are proliferating in the United States, with several available online, and some available over the counter at pharmacies.
Some are antigen tests, which detect protein fragments specific to the coronavirus. The turnaround time for results is usually very quick and, in some cases, results can be reported within 15 minutes.
Some are polymerase chain reaction (PCR) tests, in which one's sample must be sent to a laboratory for analysis. For these, the turnaround time is longer. Depending on the mail and the demand on the laboratory, it could be as short as a day or as long as two or three days.
PCR testing is considered the gold standard, detecting RNA or genetic material that is specific to the virus.
In its December assessment, California-based organisation Grand View Research in a note said: "The global Covid-19 diagnostics market size is estimated at US$84.4 billion (S$111.8 billion) in 2020 and is expected to expand at a compound annual growth rate of 3.1 per cent from 2021 to 2027. The market is driven by the rising government initiatives targeted towards the implementation of mass testing."
The federal and state governments, and large employers like Google and Amazon, are spending millions on testing their employees.
In February, the Joe Biden administration authorised the first fully over-the-counter Covid test, a rapid antigen test produced by Australian company Ellume, and would provide funding to build a factory in the US to make millions of tests every month.
In March, California Governor Gavin Newsom announced deployment of up to 3 million free rapid antigen tests to help high-needs schools safely reopen classrooms.
Prices range from US$24.95 for a Quidel QuickVue at-Home OTC Covid-19 Test Kit, which gives the result in 10 minutes, to over US$100 for tests that require a nasal or saliva sample to be sent to a laboratory.
No test is perfect and there is some margin of error, especially in an antigen test. There are occasional false positives and false negatives.
Mr Antonio Regalado, senior editor for biomedicine for MIT Technology Review, wrote in a blog post after trying several home tests that he ended up learning an important lesson: "While some people worry that home tests could miss Covid cases, the bigger problem may be just the opposite.
"These tests have 'false positive' rates of about 2 per cent, which means that if you keep using them, you'll eventually test positive, even though you don't have Covid-19."
The Food and Drug Administration (FDA) says on its website: "Even if you receive a negative result, you should keep practising preventive measures, such as distancing, washing hands, and wearing masks, to reduce the risk of spreading Covid-19."
The Binax Now test is somewhat similar to a pregnancy test, but there are more steps and the process needs some amount of care and precision. The steps need to be properly timed.
The company recommends wearing surgical gloves to avoid contamination of the swab that one must swirl around each nostril. The swab is inserted into a pocket which contains a liquid that has been unsealed from a vial and dropped into it. The chemical reaction takes 15 minutes. And the kit comes with two rounds of tests to reduce the chances of a false result. The second test must be taken 36 hours after the first, but no later than three days after.
Some tests need the user to download an app, while others may require a live consultant from the company to call in and witness the test result in order to certify it.
In the US, the FDA has not recognised all tests as valid for, say, boarding an international flight.
The company Vault offers a US$119 kit for travel to the US from Mexico, Jamaica and the Dominican Republic, with an international shipping option.
American Airlines partners several test providers and offers a VeriFLY "secure health passport app" for iOS and Android phones, which enables the uploading of negative Covid-19 test results, vaccination records and forms to get verified status for travel.
But analysts say while over-the-counter testing fills a need, the market is softening as vaccines become more widely available, and a vaccine certificate may be more relevant.
Abbott, which makes BinaxNOW, in January said it expects to sell 120 million tests in the first half of the year.
But in April Abbott reported that Covid test-related sales fell from US$2.4 billion in the fourth quarter of 2020, to $2.2 billion in the first quarter of this year, fueling speculation that the market for rapid tests is shrinking as more people get vaccinated.